1. Field of the Invention
The invention relates to surgical computer systems, including computer program products, and methods for implant planning using captured joint motion information.
2. Description of Related Art
Orthopedic joint replacement surgery may involve arthroplasty of a knee, hip, or other joint (e.g., shoulder, elbow, wrist, ankle, fingers, etc.). For example, traditional total knee arthroplasty involves a long incision, typically in a range of about 6 to 12 inches, to expose the joint for bone preparation and implantation of implant components. The invasive nature of the incision results in a lengthy recovery time for the patient. Minimally invasive surgery (MIS) reduces the incision length for a total knee replacement surgery to a range of about 4 to 6 inches. However, the smaller incision size reduces a surgeon's ability to view and access the anatomy of a joint. Consequently, the complexity of assessing proper implant position and reshaping bone increases, and accurate placement of implants may be more difficult. Inaccurate positioning of implants may lead to reduced range of motion of a joint, impingement, and subsequent dislocation. For example, one problem with total hip replacement is dislocation of a femoral implant from an acetabular cup implant caused, for example, by impingement, which in turn may be caused by inaccurate positioning of the acetabular cup implant within a pelvis.
Another drawback of both MIS and traditional orthopedic surgical approaches is that such approaches do not enhance the surgeon's inherent surgical skill in a cooperative manner. For example, some conventional techniques for joint replacement include autonomous robotic systems to aid the surgeon. Such systems, however, typically serve primarily to enhance bone machining by performing autonomous cutting with a high speed burr or by moving a drill guide into place and holding the position of the drill guide while the surgeon inserts cutting tools through the guide. Although such systems enable precise bone resections for improved implant fit and placement, they act autonomously (rather than cooperatively with the surgeon) and thus require the surgeon to cede a degree of control to the robot.
Other conventional robotic systems include robots that cooperatively interact with the surgeon. One drawback of conventional interactive robotic systems is that such systems lack the ability to adapt surgical planning and navigation in real-time to a dynamic intraoperative environment. For example, U.S. Pat. No. 7,035,716, which is hereby incorporated by reference herein in its entirety, discloses an interactive robotic system programmed with a three-dimensional virtual region of constraint that is registered to a patient. The interactive robotic system requires a relevant anatomy to be rigidly restrained and the robotic system to be fixed in a gross position and thus lacks real-time adaptability to the intraoperative scene. Moreover, a three degree of freedom arm configuration and the requirement that the surgeon manipulate the arm using a force handle results in limited flexibility and dexterity, making the robotic system unsuitable for certain MIS applications such as intraoperative implant planning.
An important aspect of implant planning concerns variations in individual anatomies. As a result of anatomical variation, there is no single implant design or orientation of implant components that provides an optimal solution for all patients. Some conventional intraoperative positioning devices for implant planning used by surgeons to align an acetabular hip implant with respect to the sagittal and coronal planes of a patient assume that the patient's pelvis and trunk are aligned in a known orientation and do not take into account individual variations in the patient's anatomy or pelvic position on the operating room table. B. F. Morrey, editor, “Reconstructive Surgery of the Joints”, chapter Joint Replacement Arthroplasty, pages 605-608, Churchill Livingston, 1996. Implant planning based on such types of conventional devices can lead to a large discrepancy between desired and actual implant placement, possibly resulting in reduced range of motion of a joint, impingement, and dislocation.
Several attempts have been made to more precisely prepare the acetabular region for hip implants. U.S. Pat. Nos. 5,880,976; 5,995,738; 6,002,859; and 6,205,411, issued to DiGioia et al. and hereby incorporated by reference herein in their entirety, are directed to biomechanical simulations of the movement of a joint containing implant models performed under a number of test positions, including a desired range of motion of the joint. Although the DiGioia patents describe a system that may offer the potential for increased accuracy and consistency in the preparation of the acetabular region to receive implants, a shortcoming of the system is that movement of the joint is only simulated. The accuracy and consistency of the actual implant results depend on how closely the simulated motion of the joint corresponds to the actual motion of the joint. Moreover, simulated joint movement does not account for actual motion of a joint with individual variations.
U.S. Pat. Nos. 5,086,401; 5,299,288; and 5,408,409, issued to Glassman et al. and hereby incorporated by reference herein in their entirety, disclose an image directed surgical robotic system for broaching a femur to accept a femoral implant using a robotic cutter system. In the system, the coordinates and structure of a joint model are determined during an intraoperative planning phase where a surgeon manually interactively selects and positions an implant relative to images of the joint into which the implant is to be implanted. Although the Glassman patents describe a system that may offer the potential for increased accuracy and consistency in the preparation of bones to receive implants, the system lacks real-time adaptability to the intraoperative scene and consistent, predictable results regardless of surgical skill level because the surgeon manually has to interact and analyze relative discrete positions of implants in a joint rather than analyzing the implants during continuous motion of the joint.
In view of the foregoing, a need exists for surgical methods and devices which can overcome the aforementioned problems so as to enable intraoperative implant planning for accurate placement and implantation of joint implants providing an improved range of motion of a joint; consistent, predictable operative results regardless of surgical skill level; sparing healthy bone in minimally invasive surgery; and reducing the need for replacement and revision surgery.